Process of making iron-chromium nickel alloys



Patented Apr. 4, 1933 PATENT OFFICE.

FREDERICK M. REGRET, OF NEW YORK, N. Y.

Pnocnss or MAKING moir-cnnomnm nrc'xnr. ALLOYS 80 Drawing.

The invention is a process of making alloys containing iron, chromium and nickel, with or without other metals. The object of the invention is to make such allo s more economically than b the meth s heretofore practised. -This 0 ject is attained by using' almost quantitatively expelled, and at least a part of the carbon in the ferrochr'ome simultaneously eliminated. The resulting alloy, containing the nickel of the matte together with the iron and chromium of the ferrochrome, and more or less carbon, is useful for many purposes, either as produced,

or after further treatment. For example,-

the alloy can be diluted with iron to produce steels of the stainless type. In making stain less steel by the process of my invention, I'

prefer to carry out the reaction between the carbon of the ferrochromeand the nickel sulphide of the matte in such manner that the ratio of carbon to chromium in the alloy thereby produced will be somewhat higher than is preferred in stainless steels; and to remove some of the carbon in a subs uent operation, as by treating the metal wit an oxidizing slag, or Bessemerizing it with commercial oxy en or air strongly enriched with oxygen. I the further treatment of the initial alloy comprises dilution with iron, the decarburizing operation can be applied either before or after such dilution. r

I prefer to compound the charge in such manner that somewhat more than one atom of carbon to two of sulphur will be present, the 1 to 2 ratio being t at in which the elements combine to form carbon disulphide. An excess of carbon favors a more complete elimination of sulphur, but it will be understood that a complete expulsion of sulphur is unnecessary, and is. in dgeneral impossible in'ferrous metallurgy; an any proportion of carbon which will give a useful product is Application filed November 18, 1880. Serial No. 496,569.

within my invention. In this connection it may be remarked that sulphur will usually be in some de ree eliminated in the decarburizing and re ning treatments to which the initial alloy will normally be subjected, while mere dilution of the initial alloy with lowsulphur iron will of course lower the percentage of sul hur.

Since t e permissible variation in the ratio of carbon to sulphur is a wide one, and slnce the ratio of chromium to carbon in ferrochromes can bevaried through a considerable range without materially increasing the cost per ound of contained chromium, the ratio of c romium to nickel in the initial alloy can be readily controlled. As will be shown in a specific example given below, it is possible so to make up the charge that after the initial alloy is refined and decarburized with the loss of some chromium, the chromium-to-nickel ratio in the final product can be made to fall at about 2 to 1, the ratio in the common 18% chromium-8% nickel stainless steel.

In carrying out the process, the finely ground materials are referably charged into an electric smelting rnace of the openarc type at a rate commensurate with the rate of reaction. For best results as regards completeness of reaction it is desirable to operate at as high a temperature as the refractory lining of the furnace will allow.

I prefer to have some lime in the charge as a slag-forming material, and it is usually advisable to emplo some fluorspar in the mix- 35 ture to impart uidit to the slag.

In the preferred em odiment of my invention, a ferrochrome-nickel alloy containing between one and two per cent of carbon is produced in the initial stage. The alloy is then transferred to a Bessemer converter and blown preferably with commercially ure oxygen or highly oxygenated air unti the carbon has been reduced to the desired oint.

Below are given examples to show t e results attainable by the above-described process:

Example I One hundred parts of high-carbon ferrolime and 25 parts of fluorspar were mixed and charged gradually into an open-arc electric furnace which contained a small bath of molten slag made up with lime and silica in the ratio of 3 parts of lime to 1 part of quartzite. The high-carbon ferrochrome contained 69.71% chromium, 1.37% silicon and 4.8 9% carbon, and was smaller than 8 mesh. The nickel matte contained 75.28% nickel and 23.70% sulphur, and was also below 8 mesh in size. The lime and fluorspar were of the usual commercial grades. The product, ferrochrome-nickel, analyzed:

. Per cent Chromium 47.03 Nickel 28.52 Carbon 1.82 Silicon 0.07 Sulphur- 0.08 Balance mostly iron Ewample I l In another run the following mixture was charged onto a small molten bath made up with lime and silica in the ratioof two parts of lime to one part of quartzite:

Parts High-carbon ferrochrome 450 Nickel matte '112 Lime 185 Fluorspar 30 The high-carbon ferrochrome, sized smaller than 8 mesh, contained 68.23% chromium, 4.96% carbon and 1.51% silicon. The nickel matte also sized smaller than 8 mesh, contained 74.90% nickel and 23.71% sulphur. The lime and fluorsparwere of the usual commercial grade. The above mixture was charged at a uniform rate, and the furnace used was an open-arc electric furnace operating at a high temperature. Upon completion of the smelting, a sample of the alloy was taken which analyzed as follows:

Percent Percent Percent Percent Percent Percent Or Nl Fe C Si 8 The molten alloy was tapped directly into a Bessemer converter and blown for 30 minutes with a blast .of commercially pure oxygen. Upon completion of the blow the alloy was cast in pig form. Analysis of the final product showed:

Percent Percent Percent Percent Percent Percent Or N! I. O B! s -Ewample I'll .The following example is illustrative of the process as applied ,to the manufacture of stainlqss steel of the 18% chromium-8% nickel variety. Materials making up the charge, proportioned as shown below, were of the same analysis and size as those employed in the immediatelypreceding example:

Parts High-carbon ferrochrome 200 Nickel matte 40 Lime Fluorspar 8 The above mixture was charged into an open-arc electric furnace, operated at a high temperature, at a uniform-rate. After completion of the smelting, 240 partsv of steel scrap were melted into the alloy, which was thereupon tapped into a Bessemer converter and blown with commercially pure oxygen for 8% minutes. From the converter, the steel was tapped into two ladles and then into ingot molds after treatment with 0.40% manganese as low carbon ferromanganese and 0.40% silicon as 50% ferrosilicon. The two ladles were separately analyzed, the average of the closely concordant analytical figures being as follows:

Percent Percent Percent Percent Percent 0r Ni 81 0 Mn The average results of ph fislical tests of the metal are shown below: were quenched from 1150" C.

Maximum stress"--- 119,300 lbs .jp er-sq. in. Yield point 30,900 lbs; 'per sq. in. Elongation 38% Reduction of area-.." 54% 0 Impact ft. lbs.-- break Erichsen' value 10.8

Brin'ell hardness 131 It is obvious that in cases where a hi her carbon content is allowable than that o the steel produced in Example III, the blow may ing such that the charge contains more than one carbon atom to each two sul hur atoms.

2. A rocess of making low-car on low-sulphur a oys containing iron, chromium and nickel which comprises reacting on nickel matte with lime and an excess-of carbon in e test pieces bon b the a oy produced by the first-mentioned the form of carbon-containing ferrochrome, and thereafter oxidizin at least a part of the residual carbon by essemerization.

3. A process of making chrome-nickel stainless steel which comprises reacting on nickel matte with lime and an excess of carbon in the form of high-carbon ferrochrome, oxidizin at least a part of the residual caressemerization, andadding iron to reaction.

4. A process of making stainless steel which comprises melting high-carbon ferrochrome with lime and nickel matte and heating the mixture until the sulphur is substantially eliminated and an alloy containing at least 1.0% of carbon is formed; raising the ratio of chromium to carbon to a value suitable for stainless steel byblowing the metal,

in the molten state, with commercially pure oxygen, and diluting the alloy with iron at any stage after the ehmination of the sulphur.

'5. The method of reducing nickel matte which comprises reacting on said matte, in

the presence of basic slag-forming material,-

thereafter oxidizing at least'a part-of the residual carbon.

8. A process of making chromium-nickel stainless steels which comprises reactin on nickel matte, in the presence of basic s agforming material, with an excess of carbon in the form of carbon containing ferrochrome, oxidizing at least a part of the residual carbon, and adding iron to the alloy produced by the last-mentioned reaction.

9. A process of making low-carbon lowsulphur alloys containing iron, chromium and nickel which comprises reacting on nickel matte, in the presence of basic slag-forming material, with an excess of carbon in the form of carbon-containing ferrochrome, and thereafter oxidizing at least a part of the residual carbon by Bessemerization.

10. A process of making chromium-nickel stainless steels which comprises reacting on nickel matte, in the presence of basic-slagforming material, with an excess of carbon in the form of carbon-containing ferrochrome, and oxidizing at least a part of the residual carbon by blowing the metal in the molten state with oxygen-enriched air.

11. A process of maln'ng chromium-nickel stainless steels which comprises reacting on nickel matte, in the presence of a basic slag, with an excess of carbon in the form or carbon-containing ferrochrome, and heating the mixture until the sulphur is substantially eliminated and an alloy containing at least 1.0% of carbon is formed; raising the ratio of chromium to carbon to a value suitable" for stainless steel by blowing the metal in the molten state with oxy en-enriched air, and diluting the alloy with iron-at any stage after the elimination of the sulphur.

In testimon whereof Iaflixm si nature.

F EnERIcK M. B c 'r. 

